Histamine

Histamine, b-imidazolethylamine is an intercellular mediator exerting potent effects on various target tissues. Histamine is stored in large amounts in metachromatic granules of mast cells and basophils, and it is one of the major mediators of immediate hypersensitivity. It is released actively from mast cells and basophils when challenged with allergens to which the allergic patient is sensitized or with non-specific histamine releasers such as IgE or pharmacological agents. Histamine is also an important mediator in the central nervous system and the gastric mucosa.